Generally, an electronic osmotic dehydrator of electrophoresis style is an apparatus for separating the moisture contained in the sludge having the dielectric (material generating an electrical induction action) property by electrophoresis generated by an electric field.
It has been known to the public that when the DC power with positive (+) polarity and the DC power with negative (−) polarity are respectively applied to the rotating drum and the caterpillar of the electro-osmotic dehydrator as operated by electrophoresis, that is to say, when the polarities of the DC power applied to the rotating drum and the caterpillar are opposite each other, an electric field (an electrical domain generating electrical induction between an object having positive (+) polarity of the DC power and an object having negative (−) polarity of the DC power) is generated in a space between the rotating drum and the caterpillar through which the sludge passes, and thereby, most of the moisture contained in the sludge passing through a section where the rotating drum and the caterpillar of the electro-osmotic dehydrator operated by electrophoresis rotate on the same path is separated into a space at the lower of the caterpillar having a spaced structure by electrophoresis and the solid sludge from which moisture is removed is separated and discharged by a filter cloth belt.
Meanwhile, in the case of the an electronic osmotic dehydrator of electrophoresis style installed in a sewage treatment plant or a manufacturing plant which discharges a large volume of foul and waste water sludge, the high DC power should be applied to it in order to increase the strength of an electric field in its dehydrating domain. However, in the dehydrating domain of an electronic osmotic dehydrator of electrophoresis style of most manufacturers using the three-phase alternating current power (including single phase alternating current) as the input power, the separate DC power supplying apparatus (transformer, battery, rectifier) for generating an electric field is required.
However, when each DC power with the opposite polarity is respectively applied to the rotating drum and the caterpillar to form an electric field in the dehydrating domain of the conventional an electronic osmotic dehydrator of electrophoresis style as described above, the DC power is applied to all the rotating sections of the caterpillar running on an endless track, and as a result, the unnecessary DC power is applied to the caterpillar running on the section where the rotating path of the caterpillar and the rotating path of the rotating drum are not the same, which causes a huge power loss problematically.
For this reason, the applicant of the present invention filed a patent application for an invention entitled “an electro-osmotic dehydrator” (K.R. Patent Application No. 10-2004-007759) having the DC power applying structure for applying the DC power of one polarity only to the section of the caterpillar where the rotating path of the rotating drum and the rotating path of the caterpillar are the same in order to enable the electric field to be generated only in the dehydrating domain of an electronic osmotic dehydrator of electrophoresis style on Feb. 6, 2004, and its patent was registered on Nov. 8, 2004 (Registration No. 10-0457628). Also, the applicant of the present invention filed a patent application for an invention entitled “an electronic dehydrator of a phase control type” (K.R. Patent Application No. 10-2005-009928) to enable a strength of the DC power to be variably controlled depending upon the sludge volume passing through the dehydrating domain or the sludge type to be treated by providing a separate phase control circuit unit to a rectifier for applying each DC power having the opposite polarity respectively to the caterpillar and the outer surface of the rotating drum of an electronic osmotic dehydrator of electrophoresis style, on Feb. 3, 2005 and its patent was registered on Nov. 8, 2005 (K.R. Patent Registration No. 10-0528579).
However, in the case of the “electro-osmotic dehydrator (K.R Patent Application No. 10-2004-007759), it has a limitation that it cannot control the strength of the DC power variably depending upon the type or the volume of the sludge passing through the de-hydrating domain because the strength of the DC power applied to the dehydrating domain is constant. In the case of “an electric dehydrator of a phase control type” (K.R. Patent Application No. 10-2005-009928), its specification does not describe explicitly the DC power applying structure where the DC power with one polarity, which is applied to the caterpillar, is applied only to the path in the case that the rotating path of the rotating drum and the rotating path of the caterpillar are the same.
On the other hand, a general rotating drum constructing an electronic osmotic dehydrator of electrophoresis style is an apparatus for generating the electric field to induce the electrophoresis while guiding the waste water sludge into the dehydrating domain along with the caterpillar. Considering the rotating drum having a structure that the DC power with one polarity is applied to the caterpillar and the DC power with opposite polarity is applied to it, the rotating drum should be made of a material having the corrosion resistance and the abrasion resistance against the waste water sludge and further having the high electric conductivity for generation of an electric field.
However, since the conventional general rotating drum constructing an electronic osmotic dehydrator of electrophoresis style has a structure formed by making a stainless material plate into a cylindrical drum, when the dehydrating work is performed on the sludge by the electrophoresis caused by the electric field generated in the dehydrating domain, the space through the sludge passes between the rotating drum and the caterpillar, the rotating drum of stainless material generates electrolysis through its electrochemical reaction with the sludge. As a result, large and small corrosions take place in the rotating drum, and further the rotating drum is heated with the coulomb heat generated by the electrophoresis at high temperature to deform the appearance of the rotating drum having a cylindrical shape. This shortens the lifetime of the rotating drum and degrades the electric conductivity of the rotating drum problematically.
Therefore, the applicant of the present invention filed a patent application for an invention entitled “an electro-osmotic dehydrator” (K.R. Patent Application No. 10-2007-046494) on May 14, 2004, relating to a structure of a rotating drum to improve corrosion resistance and abrasion resistance and electric conductivity of the rotating drum of an electronic osmotic dehydrator of electrophoresis style at the same time. That is to say, the rotating drum has a structure that a copper plate having very high electric conductivity, a titanium plate having excellent corrosion resistance and abrasion resistance and a platinum-based metal coating agent are closely stacked in order on the stainless material plate and they are fixed by fastening bolts penetrating through the stacked part, which are provided in its outer circumference at a given interval.
However, when the DC power with one polarity is applied to the rotating drum of the “electro-osmotic dehydrator (K.R. Patent Application No. 10-2007-046494), the DC power does not electrify only the platinum-based coating agent of the rotating drum but a large portion of the DC power electrified the inner copper plate of the rotating drum having very high electric conductivity through the fastening bolts penetrating through the inside of the rotating drum. Therefore, when the electric field is generated by applying the DC power to the rotating drum in the dehydrating domain, a large portion of the DC power determining the strength of the electric field gets to flow to the inner copper plate of the rotating drum having very high electric conductivity so that the strength of the DC power drops drastically on the outer surface of the rotating drum, causing an unnecessary power loss, which is a problem of the said rotating drum.